Particle extraction apparatus and particle extraction method

ABSTRACT

Provided is microparticle extraction technology capable of stably extracting only a target microparticle at high speed from a sheath flow flowing through a flow path. 
     A particle extraction apparatus includes: a first extraction unit for extracting, from a whole sample containing a target particle, an extraction sample containing the target particle without performing abort processing; and a second extraction unit for subjecting the extraction sample to abort processing and extracting only the target particle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 371 as a U.S.National Stage Entry of International Application No. PCT/JP2017/006503,filed in the Japanese Patent Office as a Receiving Office on Feb. 22,2017, which claims priority to Japanese Patent Application NumberJP2016-098927, filed in the Japanese Patent Office on May 17, 2016, eachof which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present technology relates to a particle extraction apparatus and aparticle extraction method. More specifically, the present technologyrelates to a particle extraction apparatus and the like capable ofstably extracting only a target microparticle at high speed from asheath flow flowing through a flow path.

BACKGROUND ART

As this type of particle extraction apparatus, for example, amicroparticle extraction apparatus for forming a sheath flow containinga microparticle in a flow path, irradiating the microparticle in thesheath flow with light to detect fluorescence and scattered lightgenerated from the microparticle, and separating and recovering amicroparticle group exhibiting predetermined optical characteristics isknown. For example, with a flow cytometer, by labeling a plurality ofkinds of cells contained in a sample with a fluorescent dye andoptically identifying the fluorescent dye labeled to each of the cells,only specific kinds of cells are separated and recovered.

As the flow cytometer, a so-called droplet charging type for making afluid discharged from a flow cell, a microchip, or the like into adroplet, applying a plus (+) or minus (−) charge to the droplet, andextracting a target particle as disclosed in Patent Document 1, and amicro flow path type for performing extraction in a microchip asdisclosed in Patent Document 2 are known, for example.

Such technology of the flow cytometer is expected to be utilized as aclinical application in the field of, for example, immune cell therapy.An extraction apparatus which can cope with aseptic conditions, iseasily handled, and can extract a target cell with high purity at highspeed is required. (Non-Patent Documents 1 and 2)

CITATION LIST Patent Document

-   Patent Document 1: Japanese Patent Application Laid-Open No.    2009-145213-   Patent Document 2: Japanese Patent Application Laid-Open No.    2014-036604

Non-Patent Document

-   Non-Patent Document 1: Leukemia (2016) 30, 492-500;    doi:10.1038/leu.2015.247; published online 6 Oct. 2015-   Non-Patent Document 2: Baghbaderani et al., cGMP-Manufactured Human    Induced Pluripotent Stem Cells Are Available for Preclinical and    Clinical Applications, Stem Cell Reports (2015),    http://dx.doi.org/10.1016/j.stemcr.2015.08.015

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in conventional particle extraction technology, when extractionis performed, a liquid and particles present in a certain finite volumeare taken in together. Therefore, in a case where it is attempted toextract a target particle, if a distance between the target particle anda particle spatially adjacent thereto is small, a possibility that theadjacent particle will be taken in together increases. Therefore, inorder to extract a target particle at high speed in the flow cytometer,a probability that a non-target particle is taken in together with thetarget particle increases, and a ratio (also referred to as “purity”) ofthe target particle with respect to an extracted whole sample decreasesdisadvantageously.

In addition, in a case where reduction in purity is not allowable, evenif a particle with a short passage time interval with an adjacentparticle is a target particle, it is necessary to determine not toperform extraction in a processing system (hereinafter also referred toas “abort”), a ratio (also referred to as “yield”) of the number ofextracted target particles with respect to the number of input targetparticles is reduced, and as a result, extraction cannot be performed athigh speed disadvantageously.

Furthermore, as a means for performing extraction of a particle at highspeed, a method for simultaneously driving a plurality of extractionmechanisms disposed in parallel is considered. However, in addition to asheath forming unit, for example, an excitation optical system forexciting a fluorescent dye of a dyed particle, a detection system fordetecting fluorescence, an electrical system for converting detectedlight into an electric signal with a photoelectric conversion elementand amplifying and digitizing the electric signal, a processing systemfor determining whether extraction is performed on the basis of thesignal, and the like are required in proportion to the parallel numberof the extraction mechanisms. This brings an increase in size of aparticle extraction apparatus and an increase in cost disadvantageously.

Solutions to Problems

The present technology provides a particle extraction apparatusincluding: a first extraction unit for extracting, from a whole samplecontaining a target particle, an extraction sample containing the targetparticle without performing abort processing; and a second extractionunit for subjecting the extraction sample to abort processing andextracting only the target particle.

In the particle extraction apparatus according to the presenttechnology, the first extraction unit and the second extraction unit maybe formed as separate members, and after extraction by the firstextraction unit, extraction by the second extraction unit may beperformed.

In addition, in the particle molecular apparatus according to thepresent technology, the first extraction unit and the second extractionunit may be formed as the same member, and after extraction by the firstextraction unit, extraction by the second extraction unit may beperformed.

In addition, the particle molecular apparatus according to the presenttechnology may include a stirring unit for returning a particle intervalin an extraction sample extracted by the first extraction unit to arandom state.

In addition, the particle molecular apparatus according to the presenttechnology may include: a measurement unit for measuring a ratio of atarget particle with respect to the whole sample; and an extractionswitching unit for switching an extraction operation by the firstextraction unit and an extraction operation by the second extractionunit to a parallel operation on the basis of a measurement result by themeasurement unit.

The present technology also provides a particle extraction methodincluding: a first extraction step of extracting, from a whole samplecontaining a target particle, an extraction sample containing the targetparticle without performing abort processing; and a second extractionstep of subjecting the extraction sample to abort processing andextracting only the target particle.

The particle extraction method according to the present technology mayinclude a stirring step of returning a particle interval in theextraction sample to a random state after the first extraction step isperformed.

In addition, the particle extraction method according to the presenttechnology may further include an extraction switching step ofperforming the first extraction step and the second extraction step inparallel on the basis of a ratio of a target particle with respect tothe whole sample.

Furthermore, the present technology also provides a particle extractionmicrochip including: a first extraction unit for extracting, from awhole sample containing a target particle, an extraction samplecontaining the target particle without performing abort processing; anda second extraction unit for subjecting the extraction sample to abortprocessing and extracting only the target particle.

In the present technology, the “target particle” widely includes aliving body-related microparticle such as a cell, a microorganism, or aliposome, and a synthetic particle such as a latex particle, a gelparticle, or an industrial particle.

The living body-related microparticle includes a chromosome, a liposome,a mitochondria, an organelle, and the like constituting various cells.The cells include an animal cell (such as a hemocyte cell) and a plantcell. The microorganism includes bacteria such as Escherichia coli,viruses such as tobacco mosaic virus, fungi such as yeast, and the like.Furthermore, the living body-related microparticle can also include aliving body-related polymer such as a nucleic acid, a protein, orcomplexes thereof. In addition, the industrial particles may be, forexample, an organic or inorganic polymer material or a metal. Theorganic polymer material includes polystyrene, styrene-divinylbenzene,polymethyl methacrylate, and the like. The inorganic polymer materialincludes glass, silica, a magnetic material, and the like. The metalincludes gold colloid, aluminum, and the like. The shape of each ofthese microparticles is generally spherical but may be non-spherical,and the size, mass, and the like thereof are not particularly limited,either.

Effects of the Invention

The present technology provides microparticle extraction technologycapable of stably extracting only a target microparticle at high speedfrom a sheath flow flowing through a flow path.

Note that the effects described herein are not necessarily limited, andmay be any of the effects described in the present technology.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic conceptual diagram schematically illustrating aconcept of a first embodiment of a particle extraction apparatusaccording to the present technology.

FIG. 2 is a schematic conceptual diagram schematically illustratingextraction processing in a first extraction unit included in theparticle extraction apparatus illustrated in FIG. 1.

FIG. 3 is a schematic conceptual diagram schematically illustratingextraction processing in a second extraction unit included in theparticle extraction apparatus illustrated in FIG. 1.

FIG. 4 is a schematic conceptual diagram schematically illustrating apositional relationship between a target particle and a non-targetparticle when a target particle is captured in the first extractionunit.

FIG. 5 is a schematic conceptual diagram schematically illustrating atime period during which a subsequent particle cannot be taken inimmediately after extraction in the first extraction unit.

FIG. 6 is a schematic conceptual diagram for explaining, when the firstextraction unit captures a target particle, a probability that the firstextraction unit takes in a target particle present near the targetparticle to be captured.

FIG. 7 is a schematic conceptual diagram schematically illustrating aconcept of a second embodiment of the particle extraction apparatusaccording to the present technology.

FIG. 8 is a schematic conceptual diagram schematically illustrating aconcept of a third embodiment of the particle extraction apparatusaccording to the present technology.

FIG. 9 is a schematic conceptual diagram schematically illustrating aconcept of a first embodiment of a particle extraction microchipaccording to the present technology.

FIG. 10 is a diagram for explaining the extraction operation illustratedin FIG. 9.

FIG. 11 is a diagram illustrating a function of a pressure chamberincluded in the microchip illustrated in FIG. 9.

FIG. 12 is a side view of a stirring unit of the microchip illustratedin FIG. 9.

FIG. 13 is an enlarged view illustrating details of the stirring unitincluded in the microchip illustrated in FIG. 9.

FIG. 14 is a flowchart illustrating a particle extraction method of afirst embodiment according to the present technology.

FIG. 15 is a flowchart illustrating a particle extraction method of asecond embodiment according to the present technology.

FIG. 16 is a drawing substitution graph illustrating a result ofperformance comparison between a cascade method and a parallel methodbased on parameter 1.

FIG. 17 is a drawing substitution graph illustrating a result ofperformance comparison between a cascade method and a parallel methodbased on parameter 2.

FIG. 18 is a drawing substitution graph illustrating a result ofperformance comparison between a cascade method and a parallel methodbased on parameter 3.

FIG. 19 is a drawing substitution graph illustrating a result ofperformance comparison between a cascade method and a parallel methodbased on parameter 4.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments for carrying out the presenttechnology will be described with reference to the drawings. Theembodiments described below exemplify representative embodiments of thepresent technology, and the scope of the present technology is notnarrowly interpreted by the embodiments. Note that the description willbe made in the following order.

1. Particle extraction apparatus according to first embodiment

(1) Housing unit

(2) Liquid feeding unit

-   -   (3) First extraction unit    -   (3-1) Detection system    -   (3-2) Processing system    -   (3-3) Extraction system    -   (4) Stirring unit    -   (5) Second extraction unit    -   (5-1) Extraction system    -   (6) Storage unit

2. Particle extraction apparatus according to second embodiment

-   -   (1) First valve    -   (2) Second valve    -   (3) Extraction sample housing unit

3. Particle extraction apparatus according to third embodiment

-   -   (1) First valve    -   (2) Second valve    -   (3) Third valve    -   (4) Fourth valve

4. Particle extraction microchip according to first embodiment

-   -   (1) First extraction section    -   (2) Liquid feeding section    -   (3) Second extraction section

5. Particle extraction method according to first embodiment

-   -   (1) Whole sample inflow step    -   (2) First extraction step    -   (3) Stirring step    -   (4) Second extraction step    -   (5) Target particle storing step

6. Particle extraction method according to second embodiment

1. Particle Extraction Apparatus According to First Embodiment

A first embodiment of a particle extraction apparatus according thepresent technology will be described with reference to FIGS. 1 to 6.

A particle extraction apparatus 1 according to the present technologyincludes at least a first extraction unit 11 and a second extractionunit 12. In addition, the particle extraction apparatus 1 may include astirring unit 13, a housing unit 14, a storage unit 15, and a liquidfeeding unit 16 as necessary. Each of the units will be described belowaccording to the order in which a particle flows. The particleextraction apparatus 1 performs two extraction operations includingextraction by the first extraction unit 11 and extraction by the secondextraction unit 12. Incidentally, in the particle extraction apparatus 1according to the present technology, the number of extraction is notparticularly limited as long as two or more extraction units areincluded.

(1) Housing Unit

The particle extraction apparatus 1 according to the present technologyincludes the housing unit 14. The housing unit 14 houses a whole samplecontaining a target particle as an extraction target. The configurationof the housing unit 14 is not particularly limited, and can beappropriately changed depending on a storage environment condition of atarget particle, a usage environment of a particle extraction apparatus,and the like, and a known structure can be adopted. For example, in acase where it is necessary to isolate a target particle from an externalatmosphere, various structures such as a structure in which a checkvalve or the like is provided to prevent another sample from enteringfrom the outside and a container structure in which an externalatmosphere such as a test tube is in contact with a whole sample areconsidered.

(2) Liquid Feeding Unit

The particle extraction apparatus 1 according to the present technologymay include the liquid feeding unit 16 as necessary. The liquid feedingunit 16 allows a whole sample housed in the housing unit 14 to flow intothe first extraction unit 11. As the structure of the liquid feedingunit 16, a known structure can be adopted as long as the whole samplecan be sent out to the first extraction unit 11.

For example, in a case where a tubular member (tube or the like) isconnected to the housing unit 14 and the whole sample is fed to thefirst extraction unit 11 via the tubular member, as the configuration ofthe liquid feeding unit 16, a known liquid feeding pump or the like isconsidered.

(3) First Extraction Unit

The particle extraction apparatus 1 according to the present technologyincludes the first extraction unit 11 for extracting a target samplefrom the whole sample. The first extraction unit 11 includes a detectionsystem 110 for detecting a target particle from the whole sample, anextraction system 120 for extracting the target particle on the basis ofa detection result of the detection system 110, and a processing system130 for converting detected optical information into electricinformation. Each of the systems will be described below.

(3-1) Detection System

In the first extraction unit 11 according to the present technology, thewhole sample is sent out to the detection system 110 by the liquidfeeding unit 16.

In this detection system 110, for example, a sample flow path into whichthe whole sample flows and a sheath liquid flow path into which a sheathliquid flows are formed, and a sheath flow containing a target particleis formed in the flow path.

In addition, the detection system 110 includes a labeling unit (notillustrated) for labeling the target particle in the sheath flow with afluorescent dye, an irradiation unit (not illustrated) for irradiatingthe whole sample in the sheath flow with excitation light, and a lightdetection unit (not illustrated) for detecting fluorescence and/orscattered light emitted from the target particle by irradiation withlight by the irradiation unit.

The configuration of the labeling unit is not particularly limited, anda known configuration can be adopted. In addition, the kind and thenumber of the fluorescent dye with which the labeling unit labels thetarget particle are not particularly limited, and a known dye such asfluorescein isothiocyanete (FITC: C₂₁H₁₁NO₅S), phycoerythrin (PE),periidininchlorophyll protein (PerCP), PE-Cy5, or PE-Cy7 can beappropriately selected to be used as necessary. Furthermore, eachextraction target sample may be modified with a plurality of fluorescentdyes.

In addition, the configuration of the irradiation unit is notparticularly limited, and a known configuration can be adopted. A lightsource included in the irradiation unit is not particularly limited, andexamples thereof include a semiconductor laser, that is, a laser diode,a solid laser, and a gas laser. Among these light sources, by using thesemiconductor laser, an apparatus can be small at low cost.

In addition, the wavelength of light emitted from the irradiation unitis not particularly limited, and can be appropriately changed dependingon the kind of the target particle. For example, in a case where thetarget particle is a cell, a wavelength of 300 nm or less may damage thetarget particle, and therefore it is preferable not to use thewavelength of 300 nm or less.

Furthermore, the configuration of the light detection unit is notparticularly limited, and a known configuration can be adopted. Thislight detection unit detects fluorescence and/or scattered light emittedfrom the target particle, and converts an optical signal thereof into anelectric signal. This signal conversion method is not particularlylimited, and a known method can be used. Then, the electric signaldetected by the light detection unit is output to the processing system130.

(3-2) Processing System

The processing system 130 in the first extraction unit 11 determinesoptical characteristics of an extraction sample extracted by theextraction system 120 on the basis of the input electric signal. Then,extraction information is output to the extraction system 120 such thatan extraction sample containing a target particle is extracted by theextraction system 120 depending on the optical characteristics.Meanwhile, discarding information is output to the extraction system 120such that a sample not containing a target particle is discarded.

The configuration of the processing system 130 is not particularlylimited, and the processing system 130 may be constituted by a hard diskin which a program for executing output processing of the extractioninformation and discarding information and an OS are stored, a CPU, anda memory.

(3-3) Extraction System

The extraction system 120 in the first extraction unit 11 extracts anextraction sample containing a target particle from a whole sample onthe basis of the information output from the processing system 130.

Specifically, description will be made with reference to FIG. 2. In FIG.2, the lateral direction indicates a time axis t through which a wholesample flows, the square indicates a target particle, and the triangleindicates a non-target particle. As illustrated in FIG. 2, in theextraction system 120 of the first extraction unit 11, even in a casewhere not only a target particle but also a non-target particle ispresent adjacent to the target particle while a whole sample flows, anextraction sample containing the non-target particle and the targetparticle is extracted without performing abort processing (determinationthat extraction will not be performed).

An extraction method by the extraction system 120 is not particularlylimited, and a known method can be adopted as long as an extractionsample containing a target particle is extracted without performingabort processing.

(4) Stirring Unit

The particle extraction apparatus 1 according to the present technologymay include the stirring unit 13 as necessary.

The stirring unit 13 is disposed between the first extraction unit 11and the second extraction unit 12, and changes a particle interval inthe extraction sample. Specifically, the stirring unit 13 returns theparticle interval in the extraction sample extracted by the firstextraction unit 11 to a random state as in the case of the whole sample.Then, the extraction sample in which a particle interval is in a randomstate is fed to the second extraction unit 12.

The configuration of the stirring unit 13 is not particularly limited,and a known stirrer or the like can be adopted. In a case where thefirst extraction unit 11 and the second extraction 12 are connected witha tubular member and an extraction sample flows inside the tubularmember, examples of the stirring unit 13 include a so-called peristalticdosing pump. A configuration in which this peristaltic dosing pumpcompresses and relaxes the tubular member is considered.

Incidentally, a method for stirring the extraction sample is notparticularly limited, and a known method can be adopted. Examplesthereof include a method for applying pressure to the extraction sample.

(5) Second Extraction Unit

The particle extraction apparatus 1 according to the present technologyincludes the second extraction unit 12 for extracting a target particlefrom the extraction sample. This second extraction unit 12 includes adetection system 210 for detecting a target particle from an extractionsample, an extraction system 220 for extracting a target particle on thebasis of a detection result of the detection system 210, and aprocessing system 230 for converting a detected optical signal into anelectric signal. Each of the systems will be described below.

Note that the detection system 210 has the same configuration as that ofthe detection system 110 of the first extraction unit 11 except that adetection target is an extraction sample, and therefore descriptionthereof will be omitted. In addition, the configuration of theprocessing system 230 is also the same as that of the processing system130 of the first extraction unit 11, and therefore description thereofwill be omitted.

(5-1) Extraction System

The extraction system 220 in the second extraction unit 12 extracts atarget particle from an extraction sample on the basis of informationoutput from the processing system 230.

Specifically, description will be made with reference to FIG. 3. In FIG.3, the lateral direction indicates a time axis t through which a wholesample flows, the square indicates a target particle, and the triangleindicates a non-target particle. As illustrated in FIG. 3, unlike theextraction system 120 of the first extraction unit 11, the extractionsystem 220 extracts only a target particle, and performs abortprocessing in a case of recognizing a non-target particle.

Incidentally, an extraction method by the extraction system 220 is notparticularly limited, and a known method can be adopted as long as onlya target particle is extracted.

(6) Storage Unit

The particle extraction apparatus 1 according to the present technologymay include a storage unit 16 as necessary.

This storage unit 16 stores only a target particle extracted by thesecond extraction unit 12.

The configuration of the storage unit 16 is not particularly limited,and can be appropriately changed depending on a storage environmentcondition of a target particle, a usage environment of a particleextraction apparatus, and the like, and a known structure can beadopted. For example, in a case where there is a condition that a targetparticle is easily damaged by an external environment, examples of theconfiguration of the storage unit 16 include a closed container in whicha stored target particle is not in contact with an external atmosphere.

In the particle extraction apparatus 1 according to the presenttechnology as described above, for example, two extraction operationsare performed by the first extraction unit 11 and the second extractionunit 12. Finally, a recovery ratio of a target particle (hereinafteralso referred to as “yield”) needs to be equal to or larger than adesired value.

Therefore, in the particle extraction apparatus 1 according to thepresent technology, the number of detection of a whole sample per unittime at the time of the extraction operation by the first extractionunit 11 is desirably set in relation to a final desired recovery ratioYs of a target particle.

Specifically, for example, one mode is considered in which a detectionnumber λ of a whole sample per unit time in the first extraction unit 11is set within a range satisfying the following Mathematical Formula 1.

$\begin{matrix}{Y_{cascode} = {{R \cdot \frac{1 + {\lambda_{T}{T_{P}/2}}}{1 + {\lambda_{T}\left( {{T_{P}/2} + T_{D}} \right)}} \cdot R \cdot \frac{1 + {\lambda_{T\; 2}{T_{P}/2}}}{\begin{matrix}{1 + {\lambda_{T\; 2}\left( {{T_{P}/2} + T_{D}} \right)} +} \\{\left( {1 - e^{{- \lambda_{U2}}T_{P}}} \right)/e^{{- \lambda_{U2}}T_{P}}}\end{matrix}}} \geq Y_{S}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Hereinafter, a method for calculating Mathematical Formula 1 will bedescribed with reference to FIGS. 4 to 6.

Here, as described above, the particle extraction apparatus 1 accordingto the present technology forms a sheath flow to extract a targetparticle and constitutes a so-called flow cytometer.

A performance index of this flow cytometer is defined as illustrated inthe following Table 1.

TABLE 1 Item Symbol Definition Event Rate λ detection number of a wholesample per unit time Yield Y recovery ratio with respect to a wholesample to be extracted Efficiency E extraction efficiency for a detectedtarget particle Recovery R recovery ratio of a particle that has beenextracted Purity P ratio of a target particle in an extraction sample

Hereinafter, each parameter for deriving Mathematical Formula 1 will bedescribed on the basis of the definitions illustrated in Table 1.

That is, it is generally known that in a flow cytometer, the number ofparticles passing through a detection unit per unit time follows aPoisson distribution.

Here, if the average number of passing particles per unit time isrepresented by λ, the average number of passing particles per time t isrepresented by λt. In addition, a probability that x target particlespass per time t is expressed by the following Mathematical Formula 2.

$\begin{matrix}{{P\left( {x❘t} \right)} = {e^{- {({\lambda\; t})}}\frac{\left( {\lambda\; t} \right)^{x}}{x!}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Furthermore, a probability that a target particle does not pass duringtime t can be expressed by the following Mathematical Formula 3 on thebasis of Mathematical Formula 2.

$\begin{matrix}{{P\left( {0❘t} \right)} = {{e^{- {({\lambda\; t})}}\frac{\left( {\lambda\; t} \right)^{0}}{0!}} = e^{{- \lambda}\; t}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In addition, paying attention to a certain target particle, aprobability that no particle is present in forward time T₀ of the targetparticle and that no particle is present in backward time thereof T₁ canbe expressed by the following Mathematical Formula 4 on the basis ofMathematical Formula 2.

$\begin{matrix}{{{P\left( {0❘T_{0}} \right)} \cdot {p\left( {0❘T_{1}} \right)}} = {{e^{- {\lambda T}_{0}} \cdot e^{- {\lambda T}_{1}}} = e^{- {\lambda{({T_{0} + T_{1}})}}}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 4} \right\rbrack\end{matrix}$

Furthermore, when a flow cytometer extracts a target particle, it isconsidered that the target particle (the number of passing targetparticles per unit time is represented by λ_(T)) and a non-targetparticle (the number of passing non-target particles per unit time isrepresented by λ_(U)) are mixed. In addition, in a case where a certaintarget particle is captured, considering a group of λ_(U)+1 particlesincluding the target particle and non-target particles present beforeand behind the target particle, the particles included in this group donot correlate with one another. Therefore, a probability that anon-target particle does not pass in forward time T₀ of the targetparticle and that no non-target particle does not pass in backward timethereof T₁ can be expressed by the following Mathematical Formula 5.

$\begin{matrix}{e^{{- {({\lambda_{U} + 1})}}{({T_{0} + T_{1}})}} \cong e^{- {\lambda_{U}{({T_{0} + T_{1}})}}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 5} \right\rbrack\end{matrix}$Provided that T₀+T₁<<1 is satisfied.

Next, extraction efficiency E for a detected target particle will bedescribed below with reference to FIG. 4.

Here, a time width (hereinafter referred to as “capture time width”) ofincoming particle group taken in by one extraction operation isrepresented by T_(p).

Then, in general, in order to secure a target particle ratio P in anextraction sample, a flow cytometer takes in the target particle in acase of T₀+T₁>T_(p) in FIG. 4. Meanwhile, in a case of T₀+T₁≤T_(p),determination that the target particle is not taken in (abortprocessing) is performed.

For this reason, the extraction efficiency E for a detected targetparticle can be expressed by the following Mathematical Formula 6.

$\begin{matrix}{E = e^{{- \lambda_{U}}T_{P}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 6} \right\rbrack\end{matrix}$

In addition, when a flow cytometer performs extraction, particularly ina case where a micro flow path method is adopted, as illustrated in FIG.5, a time period (hereinafter referred to as “dead time T_(D)”) in whicha subsequent particle cannot be taken in immediately after extraction)is present. Therefore, in a case where the detection number λ of a wholesample per unit time in the first extraction unit 11 of the particleextraction apparatus 1 according to the present technology is indicatedin relation to a final target particle recovery ratio Y on the basis ofMathematical Formula 1, it is also necessary to consider the dead timeT_(D).

Furthermore, in a case where a flow cytometer does not perform abortprocessing, when capturing a target particle that has reached anextraction unit, the flow cytometer may also take in a target particlepresent near the target particle to be captured.

In such a case, all the particles present in the past on the time axisas compared with a particle to be captured should have already beencaptured. Therefore, as illustrated in FIG. 6, it can be recognized thata particle which may be captured together is only a particle present ina future time width T_(p)/2 as compared with the particle to becaptured.

Therefore, considering a probability that a group of remaining λ_(r)−1target particles is mixed with respect to one target particle to becaptured in a time width of T_(p)/2, an average value of the number oftarget particles captured by one extraction operation can be expressedby the following Mathematical Formula 7.

$\begin{matrix}{{R \cdot \left( {1 + {\left( {\lambda_{T} - 1} \right){T_{P}/2}}} \right)} \cong {R \cdot \left( {1 + {\lambda_{T}{T_{P}/2}}} \right)}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 7} \right\rbrack\end{matrix}$Provided that T_(p)<<1 is satisfied.

In addition, in a case where the flow cytometer performs abortprocessing, it is necessary to consider an expected value T_(c) of timerequired for actually capturing a certain target particle after tryingto capture the target particle.

Here, an average arrival time interval of a target particle is 1/λ_(T).Therefore, if e^(−λUTP)≡E is defined, the expected value T_(c) can beexpressed by the following Mathematical Formula 8. Here, the first termof Mathematical Formula 8 represents time in a case where the firstparticle is not aborted but taken in, the second term represents time ina case where the first particle is aborted and the second particle istaken in, the third term represents time in a case where the first andsecond particles are aborted and the third particle is taken in, thefourth term represents time in a case where the first, second, and thirdparticles are aborted and the fourth particle is taken in, and the like.

$\begin{matrix}{T_{c} = {{0 \cdot E} + {\frac{1}{\lambda_{T}} \cdot E \cdot \left( {1 - E} \right)} + {\frac{2}{\lambda_{T}} \cdot E \cdot \left( {1 - E} \right) \cdot \left( {1 - E} \right)} + {\frac{3}{\lambda_{T}} \cdot E \cdot \left( {1 - E} \right) \cdot \left( {1 - E} \right) \cdot \left( {1 - E} \right)} + \ldots}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 8} \right\rbrack\end{matrix}$

On the basis of Mathematical Formula 8, the following MathematicalFormula 9 is calculated.

$\begin{matrix}\begin{matrix}{T_{c} = {{0 \cdot E} + {\frac{1}{\lambda_{T}} \cdot E \cdot \left( {1 - E} \right)} + {\frac{2}{\lambda_{T}} \cdot E \cdot \left( {1 - E} \right) \cdot}}} \\{\left( {1 - E} \right) + {\frac{3}{\lambda_{T}} \cdot E \cdot \left( {1 - E} \right) \cdot \left( {1 - E} \right) \cdot \left( {1 - E} \right)} + \ldots} \\{= {\frac{1}{\lambda_{T}} \cdot E \cdot {\left( {1 - E} \right)\left\lbrack {1 + {2\left( {1 - E} \right)} +} \right.}}} \\\left. {{3\left( {1 - E} \right)^{2}} + \ldots}\mspace{11mu} \right\rbrack \\{= {{\frac{1}{\lambda_{T}} \cdot E \cdot \left( {1 - E} \right)}\frac{1}{\left( {1 - \left( {1 - E} \right)} \right)^{2}}}} \\{= {\frac{1}{\lambda_{T}} \cdot \frac{1 - E}{E}}} \\{= {\frac{1}{\lambda_{T}} \cdot \frac{1 - e^{{- \lambda_{U}}T_{P}}}{e^{{- \lambda_{U}}T_{P}}}}}\end{matrix} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 9} \right\rbrack\end{matrix}$

Incidentally, a relational formula expressed by the followingMathematical Formula 10 was used for the calculation of MathematicalFormula 9.

$\begin{matrix}{{\left( {1 - x} \right)\left( {1 + {2x} + {3x^{2}} + \ldots}\mspace{11mu} \right)} = {{1 + x + x^{2} + \ldots} = {{\frac{1}{1 - x}\therefore{1 + {2x} + {3x^{2}} + \ldots}} = \frac{1}{\left( {1 - x} \right)^{2}}}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 10} \right\rbrack\end{matrix}$

Furthermore, as described above, in a case where the flow cytometerperforms extraction, a target particle and a non-target particle may bemixed.

Here, for example, in a case where the number of passing targetparticles per unit time when the target particles pass through the firstextraction unit 11 is represented by λ_(T), and the number of passingnon-target particles per unit time when the non-target particles passthrough the first extraction unit 11 is represented by λ_(U), a wholesample input to a particle extraction apparatus can be expressed by thefollowing Mathematical Formula 11.

$\begin{matrix}{\lambda = {\lambda_{T} + \lambda_{U}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 11} \right\rbrack\end{matrix}$

Furthermore, according to Mathematical Formula 11, a ratio r of thenumber of target particles with respect to the total number of particlescan be expressed by the following Mathematical Formula 12.

$\begin{matrix}{{r \equiv \frac{\lambda_{T}}{\lambda_{T} + \lambda_{U}}} = \frac{\lambda_{T}}{\lambda}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 12} \right\rbrack\end{matrix}$

From the above, the number λr of passing target particles per unit timewhen the target particles pass through the first extraction unit 11 andthe number λ_(U) of passing non-target particles per unit time when thenon-target particles pass through the first extraction unit 11 can beexpressed by the following Mathematical Formula 13.

$\begin{matrix}{{\lambda_{T} = {r\;\lambda}}{\lambda_{U} = {\left( {1 - r} \right)\lambda}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 13} \right\rbrack\end{matrix}$

By using the parameters expressed by Mathematical Formulas 2 to 13, itis possible to calculate a recovery ratio Y1 with respect to a wholesample to be extracted in the first extraction unit 11 according to thepresent technology.

Here, if the extraction number per unit time is represented by N, timespent for aborting is N·T_(c), and time spent for dead time is N·T_(D).Therefore, effective time contributing to extraction per unit time isrepresented by 1−N·T_(D)−N·T_(c). Therefore, an average value of thenumber of target particles captured per unit time satisfies an equationexpressed by the following Mathematical Formula 14.

$\begin{matrix}{{N \cdot R \cdot \left( {1 + {\lambda_{T}\mspace{14mu} T_{P}\text{/}2}} \right)} = {R \cdot \lambda_{T} \cdot \left( {1 - {N \cdot T_{D}} - {N \cdot T_{C}}} \right)}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 14} \right\rbrack\end{matrix}$

By converting Mathematical Formula 14, N can be expressed by thefollowing Mathematical Formula 15.

$\begin{matrix}{N = \frac{\lambda_{T}}{1 + {\lambda_{T}\left( {{T_{P}\text{/}2} + T_{D} + T_{C}} \right)}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 15} \right\rbrack\end{matrix}$

According to Mathematical Formula 15, the average value of the number oftarget particles captured per unit time can be expressed by thefollowing Mathematical Formula 16.

$\begin{matrix}{{N \cdot R \cdot \left( {1 + {\lambda_{T}\mspace{14mu} T_{P}\text{/}2}} \right)} = {R \cdot \lambda_{T} \cdot \frac{1 + {\lambda_{T}\mspace{14mu} T_{P}\text{/}2}}{1 + {\lambda_{T}\left( {{T_{P}\text{/}2} + T_{D} + T_{C}} \right)}}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 16} \right\rbrack\end{matrix}$

In addition, the first extraction unit 11 in the present technology doesnot perform abort processing. Therefore, the value of T_(c) in themathematical formula is 0, and Mathematical Formula 16 is converted intothe following Mathematical Formula 17. This value is the number λ_(T2)of target particles input to the second extraction unit 12 per unittime.

$\begin{matrix}\begin{matrix}{{N \cdot R \cdot \left( {1 + {\lambda_{T}\mspace{14mu} T_{P}\text{/}2}} \right)} =} & {R \cdot \lambda_{T} \cdot} \\ & {\frac{1 + {\lambda_{T}\mspace{14mu} T_{P}\text{/}2}}{1 + {\lambda_{T}\left( {{T_{P}\text{/}2} + T_{D} + T_{C}} \right)}}} \\{=} & {R \cdot \lambda_{T} \cdot} \\ & {\frac{1 + {\lambda_{T}\mspace{14mu} T_{P}\text{/}2}}{1 + {\lambda_{T}\left( {{T_{P}\text{/}2} + T_{D}} \right)}}} \\{\equiv} & {\lambda_{T\; 2}}\end{matrix} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 17} \right\rbrack\end{matrix}$

Similarly, the average value of the number of non-target particlescaptured per unit time can be expressed by the following MathematicalFormula 18. This value is the number λ_(U2) of target particles input tothe second extraction unit 12 per unit time.

$\begin{matrix}\begin{matrix}{{{N \cdot R \cdot \lambda_{U}}T_{P}} =} & {R \cdot \lambda_{T} \cdot \frac{\lambda_{U}T_{P}}{1 + {\lambda_{T}\left( {{T_{P}\text{/}2} + T_{D} + T_{C}} \right)}}} \\{=} & {R \cdot \lambda_{T} \cdot \frac{\lambda_{U}T_{P}}{1 + {\lambda_{T}\left( {{T_{P}\text{/}2} + T_{D}} \right)}}} \\{\equiv} & {\lambda_{U\; 2}}\end{matrix} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 18} \right\rbrack\end{matrix}$

From the above results, the recovery ratio Y1 with respect to the wholesample to be extracted in the first extraction unit 11 is a valueobtained by dividing “the number of extracted target particles(Mathematical Formula 17)” by “the number λ_(T) of target particles inan input whole sample”, and can be expressed by the followingMathematical Formula 19.

$\begin{matrix}{Y_{1} = {\frac{R \cdot \lambda_{T} \cdot \frac{1 + {\lambda_{T}\mspace{14mu} T_{P}\text{/}2}}{1 + {\lambda_{T}\left( {{T_{P}\text{/}2} + T_{D}} \right)}}}{\lambda_{T}} = {R \cdot \frac{1 + {\lambda_{T}\mspace{14mu} T_{P}\text{/}2}}{1 + {\lambda_{T}\left( {{T_{P}\text{/}2} + T_{D}} \right)}}}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 19} \right\rbrack\end{matrix}$

Next, a recovery ratio Y2 of a target particle with respect to anextraction sample to be extracted in the second extraction unit 12 iscalculated.

First, an average value of the number of target particles captured perunit time satisfies an equation expressed by the following MathematicalFormula 20.

$\begin{matrix}{{N \cdot R \cdot \left( {1 + {\lambda_{T\; 2}\mspace{14mu} T_{P}\text{/}2}} \right)} = {R \cdot \lambda_{T\; 2} \cdot \left( {1 - {N \cdot T_{D}} - {N \cdot T_{C}}} \right)}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 20} \right\rbrack\end{matrix}$

By converting Mathematical Formula 20, N can be expressed by thefollowing Mathematical Formula 21.

$\begin{matrix}{N = \frac{\lambda_{T\; 2}}{1 + {\lambda_{T\; 2}\left( {{T_{P}\text{/}2} + T_{D} + T_{C}} \right)}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 21} \right\rbrack\end{matrix}$

According to Mathematical Formula 21, the average value of the number oftarget particles captured per unit time can be expressed by thefollowing Mathematical Formula 22.

$\begin{matrix}{{N \cdot R \cdot \left( {1 + {\lambda_{T\; 2}\mspace{14mu} T_{P}\text{/}2}} \right)} = {R \cdot \lambda_{T\; 2} \cdot \frac{1 + {\lambda_{T\; 2}\mspace{14mu} T_{P}\text{/}2}}{1 + {\lambda_{T}\left( {{T_{P}\text{/}2} + T_{D} + T_{C}} \right)}}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 22} \right\rbrack\end{matrix}$

The recovery ratio Y2 in the second extraction unit 12 is a valueobtained by dividing “the number of extracted target particles(Mathematical Formula 22)” by “the number λ_(T2) of target particles inan input whole sample”.

Therefore, the recovery ratio Y2 can be expressed by the followingMathematical Formula 23.

$\begin{matrix}\begin{matrix}{Y_{2} = \frac{R \cdot \lambda_{T\; 2} \cdot \frac{1 + {\lambda_{T\; 2}\mspace{14mu} T_{P}\text{/}2}}{1 + {\lambda_{T\; 2}\left( {{T_{P}\text{/}2} + T_{D} + T_{C}} \right)}}}{\lambda_{T\; 2}}} \\{= {R \cdot \frac{1 + {\lambda_{T\; 2}\mspace{14mu} T_{P}\text{/}2}}{1 + {\lambda_{T\; 2}\left( {{T_{P}\text{/}2} + T_{D} + T_{C}} \right)}}}} \\{= {R \cdot \frac{1 + {\lambda_{T\; 2}\mspace{14mu} T_{P}\text{/}2}}{\begin{matrix}{1 + {\lambda_{T\; 2}\left( {{T_{P}\text{/}2} + T_{D}} \right)} +} \\{\left( {1 - e^{{- \lambda_{U\; 2}}T_{P}}} \right)\text{/}e^{{- \lambda_{U\; 2}}T_{P}}}\end{matrix}}}}\end{matrix} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 23} \right\rbrack\end{matrix}$

Provided that

$T_{C} = {\frac{1}{\lambda_{T}} \cdot \frac{1 - e^{{- \lambda_{U}}T_{P}}}{e^{{- \lambda_{U}}T_{P}}}}$was used.

In the particle extraction apparatus 1 according to the presenttechnology, extraction by the first extraction unit 11 and extraction bythe second extraction unit 12 are performed. Therefore, a recovery ratioY_(Cascode) of a target particle by extraction of the particleextraction apparatus 1 is a value obtained by multiplying the recoveryratio Y1 in the first extraction unit 11 by the recovery ratio Y2 in thesecond extraction unit 12 as illustrated in the following MathematicalFormula 24.

$\begin{matrix}{Y_{Cascode} = {{Y_{1}Y_{2}} = {R \cdot \frac{1 + {\lambda_{T\; 2}\mspace{14mu} T_{P}\text{/}2}}{1 + {\lambda_{T\; 2}\left( {{T_{P}\text{/}2} + T_{D}} \right)}} \cdot R \cdot \frac{1 + {\lambda_{T\; 2}\mspace{14mu} T_{P}\text{/}2}}{\begin{matrix}{1 + {\lambda_{T\; 2}\left( {{T_{P}\text{/}2} + T_{D}} \right)} +} \\{\left( {1 - e^{{- \lambda_{U\; 2}}T_{P}}} \right)\text{/}e^{{- \lambda_{U\; 2}}T_{P}}}\end{matrix}}}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 24} \right\rbrack\end{matrix}$

According to Mathematical Formula 24, in the particle extractionapparatus 1 according to the present technology, the recovery ratioY_(Cascode) is preferably equal to or higher than the final desiredrecovery ratio Ys of a target particle.

The particle extraction apparatus 1 according to the present technologyconfigured as described above includes the first extraction unit 11 andthe second extraction unit 12, includes a plurality of components forperforming extraction, and therefore can extract a target particle athigh speed with high purity.

In addition, the particle extraction apparatus 1 can perform anextraction operation superimposed by the first extraction unit 11 andthe second extraction unit 12, and is not configured so as to simplydispose a plurality of extraction mechanisms. Therefore, an increase insize of the particle extraction apparatus and an increase in cost can beavoided as much as possible.

Furthermore, by setting the detection number λ of a whole sample perunit time in the first extraction unit 11 such that the recovery ratioY_(Cascode) is equal to or higher than the final desired recovery ratioYs of a target particle, the particle extraction apparatus 1 accordingto the present technology can extract the target particle with higherpurity.

2. Particle Extraction Apparatus According to Second Embodiment

Next, a second embodiment of the particle extraction apparatus accordingto the present technology will be described with reference to FIG. 7.

In the particle extraction apparatus 1 according to the presenttechnology, illustrated in FIG. 1 or the like, the first extraction unit11 and the second extraction unit 12 are configured as separate members.However, in a particle extraction apparatus 2 according the secondembodiment, the first extraction unit 11 and the second extraction unit12 are formed as the same member, and a single extraction unit 21 hasthe functions of the first extraction unit 11 and the second extractionunit 12 according to the first embodiment. Along with this, the particleextraction apparatus 2 includes a first valve 22, a second valve 23, andan extraction sample housing unit 24 for circulating a target particle.

Hereinafter, a configuration different from the particle extractionapparatus 1 according to the first embodiment, that is, theconfigurations of the first valve 22, the second valve 23, and theextraction sample housing unit 24 will be mainly described, and acomponent common to the particle extraction apparatus 1 according to thefirst embodiment will be denoted by the same reference numeral, anddescription thereof will be omitted.

Incidentally, since the configuration of the single extraction unit ofthe present embodiment is the same as that of each of the firstextraction unit 11 and the second extraction unit 12 of the particleextraction apparatus 1 according to the first embodiment, descriptionthereof will also be omitted.

(1) First Valve

The particle extraction apparatus 2 according to the second embodimentincludes the first valve 22 on a flow path through which a whole samplecontaining a target particle flows. This first valve 22 is disposed in aconnection region between a flow path L for sending the whole sample tothe extraction unit 21 and a flow path M through which a particleextracted by the extraction unit 21 flows, and includes on-off valves 22a and 22 b disposed on the flow path L and an on-off valve 22 c disposedon the flow path M.

(2) Second Valve

The particle extraction apparatus 2 includes the second valve 23 on aflow path through which a particle extracted by the extraction unit 21flows. The second valve 23 is disposed in a connection region among aflow path N through which a particle extracted by the extraction unit 21flows, a flow path O connected to the storage unit 15, and the flow pathM, and includes an on-off valve 23 a disposed on the flow path M, anon-off valve 23 b disposed on the flow path N, and an on-off valve 23 cdisposed on the flow path O.

(3) Extraction Sample Housing Unit

The particle extraction apparatus 2 according to the second embodimentincludes the extraction sample housing unit 24 connected to the flowpath M. This extraction sample housing unit 24 is connected to the flowpath M, and therefore houses the extraction sample extracted by theextraction unit 21.

In addition, in the particle extraction apparatus 2 according to thesecond embodiment, the extraction sample housing unit 24 stirs anextraction sample and returns a particle interval in the extractionsample to a random state. That is, in the particle extraction apparatus2 according to the second embodiment, the extraction sample housing unit24 also functions as the stirring unit 13 according to the firstembodiment.

The configuration of this extraction sample housing unit 24 is notparticularly limited, and can be appropriately changed depending on astorage environment condition of a target particle, a usage environmentof a particle extraction apparatus, and the like, and a known structurecan be adopted.

In such a particle extraction apparatus 2 according to the secondembodiment, first, the on-off valves 22 a and 22 b of the first valve 22are opened, and the on-off valve 22 c is closed. In addition, the on-offvalves 23 a and 23 b of the second valve 23 are opened, and the on-offvalve 23 c is closed.

By driving a liquid feeding unit 16 in such a state, a whole sample in ahousing unit 14 is fed to the extraction unit 21.

Thereafter, the extraction unit 21 functions in the same manner as thefirst extraction unit 11 of the first embodiment, and extracts anextraction sample containing a target particle from the whole sample.Then, the extracted extraction sample flows through the flow paths N andM, and is finally housed in the extraction sample housing unit 24.Furthermore, the extraction sample is stirred in the extraction samplehousing unit 24, and the particle interval in the extraction sample isreturned to a random state.

Thereafter, the on-off valve 22 a of the first valve 22 is closed, theon-off valves 22 b and 22 c are opened, the on-off valve 23 a of thesecond valve 23 is closed, and the on-off valves 23 b and 23 c areopened.

By driving the liquid feeding unit 16 in such a state, the extractionsample in the extraction sample housing unit 24 flows through the flowpath M and the flow path L and flows into the extraction unit 21 again.

In this case, the extraction unit 21 functions in the same manner as thesecond extraction unit 12 of the first embodiment and extracts a targetparticle from the extraction sample. Then, the extracted target particleflows through the flow path N and the flow path O and is stored in thestorage unit 15.

That is, in the particle extraction apparatus 2 according to the secondembodiment, the target particle circulates through the flow paths L, N,and M, and extraction is performed twice.

Even with such a particle extraction apparatus 2, a target particle canbe extracted at high speed with high purity. In addition, the particleextraction apparatus 2 is not configured so as to simply dispose aplurality of extraction mechanisms. Therefore, an increase in size ofthe particle extraction apparatus and an increase in cost can be avoidedas much as possible.

Furthermore, by setting a detection number λ of a whole sample per unittime in the extraction unit 21 in the first cycle such that a recoveryratio Y_(Cascode) is equal to or higher than a final desired recoveryratio Ys of a target particle, the particle extraction apparatus 2according to the present technology can extract the target particle withhigher purity.

Incidentally, the configurations of the first valve 22 and the secondvalve 23 illustrated in FIG. 7 are merely examples. Anotherconfiguration may be adopted as long as a target particle circulatesthrough the flow paths L, N, and M and extraction is performed aplurality of times.

3. Particle Extraction Apparatus According to Third Embodiment

Next, a third embodiment of the particle extraction apparatus accordingto the present technology will be described with reference to FIG. 8.

Here, in a case where a ratio of a target particle in a whole sample islower than a predetermined threshold value, as in the particleextraction apparatuses 1 and 2 according to the first and secondembodiments, extraction is preferably performed in a cascade manner bythe first extraction unit 11 and the second extraction unit 12(hereinafter referred to as “cascade method”). Meanwhile, in a casewhere the ratio of a target particle in a whole sample is higher thanthe predetermined threshold value, extraction by the first extractionunit 11 and extraction by the second extraction unit 12 are suitablyperformed in parallel for performing extraction at high speed(hereinafter referred to as “parallel method”).

Therefore, in the particle extraction apparatus 3 according to the thirdembodiment, it is possible to switch between the extraction method by afirst extraction unit 11 and the extraction method by a secondextraction unit 12 depending on a ratio of a target particle in a wholesample. Along with this, the particle extraction apparatus 3 includes afirst valve 31, a second valve 32, a third valve 33, and a fourth valve34.

Hereinafter, a configuration different from the particle extractionapparatus 1 according to the first embodiment will be mainly described,and a component common to the particle extraction apparatus 1 accordingto the first embodiment will be denoted by the same reference numeral,and description thereof will be omitted.

In the particle extraction apparatus 3 according to the thirdembodiment, a small amount of sample is caused to flow in a detectionsystem 110 in advance, and the detection system 110 measures a ratio ofa target particle in a whole sample.

Incidentally, in a case where a user can recognize a ratio of a targetparticle in a whole sample, the detection system 110 does not need tomeasure the ratio of a target particle in a whole sample in advance.

(1) First Valve

The particle extraction apparatus 3 according to the third embodimentincludes the first valve 31. This first valve 31 is disposed on a flowpath L connecting the housing unit 14 to a stirring unit 13. Inaddition, the first valve 31 opens and closes the flow path L dependingon a ratio of a target particle in a whole sample.

The configuration of the first valve 31 is not particularly limited aslong as being able to open and close the flow path L, and a known on-offvalve or the like can be adopted.

(2) Second Valve

The particle extraction apparatus 3 according to the third embodimentincludes the second valve 32. The second valve 32 is disposed on a flowpath N branching from the flow path M connecting the second extractionunit 12 to a storage unit 15 and connected to the stirring unit 13. Inaddition, the second valve 32 opens and closes the flow path N dependingon a ratio of a target particle in a whole sample.

The configuration of the second valve 32 is not particularly limited aslong as being able to open and close the flow path N, and a known on-offvalve or the like can be adopted.

(3) Third Valve

The particle extraction apparatus 3 according to the third embodimentincludes the third valve 33. The third valve 33 is disposed in aconnecting region between the flow path L and a flow path O branchingfrom the flow path L and connected to the second extraction unit 12, andincludes on-off valves 33 a and 33 c disposed on the flow path L and anon-off valve 33 b disposed on the flow path O.

(4) Fourth Valve

The particle extraction apparatus 3 according to the third embodimentalso includes the fourth valve 34. The fourth valve 34 is disposed in aconnecting region between the flow path N and a flow path P branchingfrom the flow path N and connected to the first extraction unit 11, andincludes on-off valves 34 a and 34 c disposed on the flow path N and anon-off valve 34 b disposed on the flow path P.

In such a particle extraction apparatus 3 according to the thirdembodiment, in a case where a ratio of a target particle in a wholesample is lower than a threshold value (target particle ratio at which arecovery ratio Y_(Parallel) in the cascade method and the recovery ratioY_(Cascode) in the parallel method are equal to each other), the firstvalve 31 and the closing valve 33 a of the third valve 33 are closed toclose the flow path L. In addition, the second valve 32 and the closingvalve 34 a of the fourth valve 34 are closed to close the flow path N.

As a result, a whole sample containing a target particle is sent to thefirst extraction unit 11 by driving of the liquid feeding unit 16. Then,the first extraction unit 11 extracts only an extraction sample from thewhole sample.

This extraction sample flows in order of the flow path P, the stirringunit 13, and the flow path O, and flows into the second extraction unit12. Then, the second extraction unit 12 extracts only a target samplefrom the extraction sample, and the target particle flows through theflow path M and is stored in the storage unit 15.

In such a case, since the configuration is the same as that of theparticle extraction apparatus 1 according to the first embodiment, thedetection number λ of the whole sample per unit time in the firstextraction unit 11 is preferably set within a range satisfying thefollowing Mathematical Formula 25.

$\begin{matrix}{Y_{Cascode} = {{R \cdot \frac{1 + {\lambda_{T\; 2}\mspace{14mu} T_{P}\text{/}2}}{1 + {\lambda_{T\; 2}\left( {{T_{P}\text{/}2} + T_{D}} \right)}} \cdot R \cdot \frac{1 + {\lambda_{T\; 2}\mspace{14mu} T_{P}\text{/}2}}{\begin{matrix}{1 + {\lambda_{T\; 2}\left( {{T_{P}\text{/}2} + T_{D}} \right)} +} \\{\left( {1 - e^{{- \lambda_{U\; 2}}T_{P}}} \right)\text{/}e^{{- \lambda_{U\; 2}}T_{P}}}\end{matrix}}} \geq Y_{S}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 25} \right\rbrack\end{matrix}$

Meanwhile, in a case where the ratio of the target particle in the wholesample is higher than the threshold value, the first valve 31 is opened,the on-off valve 33 c in the third valve 33 is closed, and the on-offvalves 33 a and 33 b are opened. As a result, the flow path L and theflow path O communicate with each other.

In addition, the second valve 31 is opened, the on-off valve 34 c in thefourth valve 34 is closed, and the on-off valves 34 a and 34 b areopened. As a result, the flow path P, the flow path N, and the flow pathM communicate with one another.

By performing setting in this manner, the whole sample discharged fromthe housing unit 14 by driving of the liquid feeding unit 16 is suppliedat the same time as extraction by the first extraction unit 11 andextraction by the second extraction unit 12. Finally, the targetparticle extracted by each of the extraction units 11 and 12 is storedin the storage unit 15.

Here, if the extraction number per unit time is represented by N, timespent for aborting is N·T_(c), and time spent for dead time is N·T_(D).Therefore, effective time contributing to extraction per unit time isrepresented by 1−N·T_(D)−N·T_(c). Therefore, an average value of thenumber of target particles captured per unit time satisfies an equationexpressed by the following Mathematical Formula 26.

$\begin{matrix}{{N \cdot R \cdot \left( {1 + {\lambda_{T}T_{P}\text{/}2}} \right)} = {R \cdot \lambda_{T} \cdot \left( {1 - {N \cdot T_{D}} - {N \cdot T_{C}}} \right)}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 26} \right\rbrack\end{matrix}$

By converting the Mathematical Formula 26, N can be expressed by thefollowing Mathematical Formula 27.

$\begin{matrix}{N = \frac{\lambda_{T}}{1 + {\lambda_{T}\left( {{T_{P}\text{/}2} + T_{D} + T_{C}} \right)}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 27} \right\rbrack\end{matrix}$

According to the Mathematical Formula 27, the average value of thenumber of target particles captured per unit time can be expressed bythe following Mathematical Formula 28.

$\begin{matrix}{{N \cdot R \cdot \left( {1 + {\lambda_{T}{T_{P}/2}}} \right)} = {R \cdot \lambda_{T} \cdot \frac{1 + {\lambda_{T}{T_{P}/2}}}{1 + {\lambda_{T}\left( {{T_{P}/2} + T_{D} + T_{C}} \right)}}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 28} \right\rbrack\end{matrix}$

Here, a recovery ratio in one extraction can be defined as a valueobtained by dividing “the number of extracted target particles(Mathematical Formula 28)” by “the number λ_(T) of target particles inan input whole sample”. Therefore, the recovery ratio Y can be expressedby the following Mathematical Formula 29.

$\begin{matrix}\begin{matrix}{Y = \frac{R \cdot \lambda_{T} \cdot \frac{1 + {\lambda_{T}{T_{P}/2}}}{1 + {\lambda_{T}\left( {{T_{P}/2} + T_{D} + T_{C}} \right)}}}{\lambda_{T}}} \\{= {R \cdot \frac{1 + {\lambda_{T}{T_{P}/2}}}{1 + {\lambda_{T}\left( {{T_{P}/2} + T_{D} + T_{C}} \right)}}}} \\{= {R \cdot \frac{1 + {\lambda_{T}{T_{P}/2}}}{\begin{matrix}{1 + {\lambda_{T}\left( {{T_{P}/2} + T_{D}} \right)} +} \\{\left( {1 - e^{{- \lambda_{U}}T_{P}}} \right)/e^{{- \lambda_{U}}T_{P}}}\end{matrix}}}}\end{matrix} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 29} \right\rbrack\end{matrix}$

In addition, in a parallel method, if the parallel number is representedby M, λ_(T) and Δ_(U) in Mathematical Formula 29 can be replaced withΔ_(T)/M and λ_(U)/M, respectively. As a result, the recovery ratioY_(Parallel) in the case of the parallel method can be represented bythe following Mathematical Formula 30.

$\begin{matrix}{Y = {R \cdot \frac{M + {\lambda_{T}{T_{P}/2}}}{\begin{matrix}{M + {\lambda_{T}\left( {{T_{P}/2} + T_{D}} \right)} +} \\{M \cdot {\left( {1 - e^{{- \lambda_{U}}{T_{P}/M}}} \right)/e^{{- \lambda_{U}}{T_{P}/M}}}}\end{matrix}}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 30} \right\rbrack\end{matrix}$

From the above, in the particle extraction apparatus 3 according to thethird embodiment, in a case where the parallel method is adopted, thedetection number λ of a whole sample per unit time in each of theextraction units 11 and 12 is preferably set such that the recoveryratio Y_(Parallel) by the extraction units 11 and 12 is equal to orhigher than the final desired recovery ratio Ys of a target particle asexpressed by the following Mathematical Formula 31.

$\begin{matrix}{Y_{Parallel} = {{R \cdot \frac{M + {\lambda_{T}{T_{P}/2}}}{\begin{matrix}{M + {\lambda_{T}\left( {{T_{P}/2} + T_{D}} \right)} +} \\{M \cdot {\left( {1 - e^{{- \lambda_{U}}{T_{P}/M}}} \right)/e^{{- \lambda_{U}}{T_{P}/M}}}}\end{matrix}}} \geq Y_{S}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 31} \right\rbrack\end{matrix}$

A switching reference between the cascade method and the parallel methodwill be described more specifically. In a case where a maximum eventrate satisfying the Mathematical Formula 30 is represented by“λ_(Parallel_max)” and a maximum event rate satisfying the MathematicalFormula 25 is represented by “λ_(cascode_max)”, in a case of thecondition of the following Mathematical Formula 32, the parallel methodis selected. Meanwhile, in a case of the condition of the followingMathematical Formula 33, the cascade method is selected.

$\begin{matrix}{\lambda_{{Parallel}\;{\_\max}} \geq \lambda_{{Cascode}\;{\_\max}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 32} \right\rbrack\end{matrix}$

$\begin{matrix}{\lambda_{{Parallel}\;{\_\max}} < \lambda_{{Cascode}\;{\_\max}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 33} \right\rbrack\end{matrix}$

Such a particle extraction apparatus 3 according to the third embodimentswitches between the cascade method and the parallel method by openingand closing the first valve 31, the second valve 32, the third valve 33,and the fourth valve 34.

That is, the first valve 31, the second valve 32, the third valve 33,and the fourth valve 34 correspond to an extraction switching unitaccording to the present technology.

The particle extraction apparatus 3 according to the third embodiment asdescribed above can switch between the parallel method and the cascademethod, and therefore can extract a target particle with high purity athigh speed depending on a ratio of a target particle in a whole sample.

Furthermore, in a case where the cascade method is selected, theparticle extraction apparatus 3 can extract a target particle at highspeed with high purity. In addition, the particle extraction apparatus 3is not configured so as to simply dispose a plurality of extractionmechanisms. Therefore, an increase in size of the particle extractionapparatus and an increase in cost can be avoided as much as possible. Inaddition, by setting the detection number λ of a whole sample per unittime in the first extraction unit 11 such that the recovery ratioY_(Cascode) is equal to or higher than the final desired recovery ratioYs of a target particle, the particle extraction apparatus 3 accordingto the present technology can extract the target particle with higherpurity.

Meanwhile, even in a case where the parallel method is selected, theparticle extraction apparatus 3 can extract a target particle at highspeed with high purity. In addition, the particle extraction apparatus 3is not configured so as to simply dispose a plurality of extractionmechanisms. Therefore, an increase in size of the particle extractionapparatus and an increase in cost can be avoided as much as possible.

4. Particle Extraction Microchip According to First Embodiment

The present technology also provides a particle extraction microchip.

A particle extraction microchip according a first embodiment of thepresent technology will be described with reference to FIGS. 9 to 13.

A particle extraction microchip 4 (hereinafter also referred to as“microchip”) according to the present technology includes a firstextraction section A for extracting an extraction sample containing atarget particle from a whole sample, a liquid feeding section 4B forfeeding the extraction sample extracted in the first extraction section4A, and a second extraction section 4C for extracting only a targetparticle from the extraction sample. The configuration of each of thesections will be described below.

(1) First Extraction Section

The microchip 4 includes a sample inlet 41 for introducing a wholesample containing a target particle. This sample inlet 41 is connectedto a sample flow path 42 through which the whole sample flows. Inaddition, this microchip 4 includes a sheath liquid inlet 43 forintroducing a sheath liquid. This sheath liquid inlet 43 branches intotwo sheath liquid flow paths 44 and 44, and the sheath liquid flowsthrough these sheath liquid flow paths 44 and 44. Furthermore, thesesheath liquid flow paths 44 and 44 join the sample flow path 42 to formone main flow path 45. In this main flow path 45, a laminar flow of awhole sample fed through the sample flow path 42 joins sheath liquidlaminar flows fed through the sheath liquid flow paths 44 and 44 to forma sheath flow in which the laminar flow of the whole sample issandwiched between the sheath liquid laminar flows.

In addition, in the main flow path 45, an irradiation unit 7A irradiatesa whole sample flowing in the main flow path 45, particularly a targetparticle with excitation light. Fluorescence and/or scattered lightemitted from the whole sample by this irradiation with light is detectedby a light detection unit 8A. An optical signal detected by this lightdetection unit 8A is converted into an electric signal and output to adriving unit 9A. This driving unit 9A adjusts pressure in a pressurechamber 47 described later and exhibits a function of sending anextraction sample containing a target particle to the pressure chamber47. Processing performed by the driving unit 9A will be described later.

Furthermore, the main flow path 45 branches into three flow paths on adownstream side. Specifically, the main flow path 45 branches into anextraction flow path 46 and two discarding flow paths 48 and 48. Amongthese flow paths, the extraction flow path 46 is a flow path for takingin an extraction sample which contains a target particle and which hasbeen determined to satisfy predetermined optical characteristics by thedriving unit 9A. In addition, the pressure chamber 47 for taking in anextraction sample containing a target particle is disposed on adownstream side of the extraction flow path 46. An inner space of thispressure chamber 47 is expanded in a planar direction (width directionof the extraction flow path 46) and also expanded in a cross-sectionaldirection (height direction of the extraction flow path 46). That is,the pressure chamber 47 is formed such that a cross sectionperpendicular to a flow direction of a whole sample and a sheath liquidis large.

Meanwhile, a whole sample not containing a target particle, which hasbeen determined not to satisfy the predetermined optical characteristicsby the driving unit 9A, is not taken in the extraction flow path 46, andflows through either one of the two discarding flow paths 48 and 48.Thereafter, the whole sample not containing the target particle isdischarged to the outside through a discarding port 49.

That is, in a microchip 101, the irradiation unit 7A, the lightdetection unit 8A, the driving unit 9A, the extraction flow path 46, andthe pressure chamber 47 correspond to the first extraction unit of thepresent technology, and exhibits the same function as the firstextraction unit 11 of the particle extraction apparatus 1 illustrated inFIG. 1.

A target particle is taken in the extraction flow path 46 by generatinga negative pressure in the extraction flow path 46 by the driving unit9A and sucking the target particle into the extraction flow path 46using this negative pressure. As a configuration for generating anegative pressure, an actuator for increasing and decreasing the volumeof the pressure chamber 47 is considered. For example, a piezoelectricelement such as a piezo element is considered.

The actuator generates a stretching force along with a change in appliedvoltage and changes a pressure in the pressure chamber 47. When flowingoccurs in the extraction flow path 46 along with this change, the volumein the extraction flow path 46 changes at the same time. The volume inthe extraction flow path 46 changes until reaching a volume defined by adisplacement amount of the actuator corresponding to an applied voltage.

Hereinafter, with reference to FIGS. 10 and 11, extraction will bedescribed in detail with the driving unit 9A.

The driving unit 9A determines optical characteristics of a wholesample, particularly a target particle on the basis of an input electricsignal. In a case where a particle is determined to be a targetparticle, as illustrated in FIGS. 10A and 10B, after time (delay time)required for an extraction sample containing the target particle to movefrom the main flow path 45 to a branching portion elapses, the drivingunit 9A outputs a drive signal for acquiring the extraction sample tothe actuator.

Specifically, in a case where the actuator is a piezo element, byapplying a voltage that causes piezo contraction, increasing the volumeof the pressure chamber 47, and setting the internal pressure of theextraction flow path 46 to a negative pressure, the driving unit 9Atakes the extraction sample in the extraction flow path 46 from theinside of the main flow path 45.

Meanwhile, in a case where a microparticle is determined to be anon-target particle, the driving unit 9A outputs a drive signal for notacquiring the non-target particle to the actuator as illustrated inFIGS. 10C and 10D. In such a case, the actuator does not operate, andthe non-target particle flows through either one of the two discardingflow paths 48 and 48.

The driving unit 9A repeats determination of optical characteristics ofthe target particle and output of a drive signal to the actuator untilanalysis is completed (see FIGS. 10E and 10F), and accumulates only anextraction sample containing the target particle in the extraction flowpath 46 (see FIG. 10F).

The target particle which has been taken in the extraction flow path 46is taken in the pressure chamber 47 as illustrated in FIG. 11A. In thefigure, the reference numeral P indicates an extraction sample which hasbeen taken in the pressure chamber 47, and the reference numeral 47 aindicates an intake port of the extraction sample P to the pressurechamber 47. A flow of the extraction sample P becomes a jet when flowinginto the pressure chamber 47 in which the inner space is expanded, andis separated from a flow path wall surface (see the arrow in FIG. 11A).For this reason, the extraction sample P leaves the intake port 47 a andtaken in the pressure chamber 47 to the back thereof.

As described above, the first extraction section 4A exhibits the samefunction as the first extraction unit 11 illustrated in FIG. 1.Therefore, a detection number λ of a whole sample per unit time in thefirst extraction section 4A is preferably set within a range satisfyingthe following Mathematical Formula 34.

$\begin{matrix}{Y_{Cascode} = {{R \cdot \frac{1 + {\lambda_{T}{T_{P}/2}}}{1 + {\lambda_{T}\left( {{T_{P}/2} + T_{D}} \right)}} \cdot R \cdot \frac{1 + {\lambda_{T\; 2}{T_{P}/2}}}{\begin{matrix}{1 + {\lambda_{T\; 2}\left( {{T_{P}/2} + T_{D}} \right)} +} \\{\left( {1 - e^{{- \lambda_{U\; 2}}T_{P}}} \right)/e^{{- \lambda_{U\; 2}}T_{P}}}\end{matrix}}} \geq Y_{S}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 34} \right\rbrack\end{matrix}$

(2) Liquid Feeding Section

Next, the liquid feeding section 4B will be described. This liquidfeeding section 4B includes an extraction sample flow path 51 connectedto the pressure chamber 47 disposed in the first extraction section 4A,a stirring unit 52 for stirring an extraction sample, a discharge flowpath 53 through which the extraction sample that has flowed through thestirring unit 52 flows, and two dampers 54 and 54 disposed on theextraction sample flow path 51 and the discharge flow path 53.

In this liquid feeding section 4B, a function of feeding the extractionsample flowing out from the first extraction section 4A is exhibited,and furthermore, in the stirring unit 52, a particle interval of theextraction sample is in a random state again as in the case of the wholesample.

The extraction sample flow path 51 is connected to the pressure chamber47, and the extraction sample extracted in the first extraction section4A is fed. Then, the extraction sample that has flowed through theextraction flow path 51 is fed into the stirring unit 52.

Next, the stirring unit 52 for stirring the extraction sample will bedescribed with reference to FIGS. 12 and 13.

The stirring unit 52 adopts the configuration a so-called peristalticdosing pump, and includes a stirring flow path 55 connected to theextraction sample flow path 51 and the discharge flow path 53, and arotary disc 56 for performing compression and relaxation of the stirringflow path 55. The stirring flow path 55 is curved into a substantially Ushape in a plan view in a circumferential direction around a rotationaxis S of the rotary disc 56.

Meanwhile, the rotary disc 56 can be rotationally driven in a directionof the arrow X around the rotation axis S. This rotary disc 56 includesthree rollers 57 disposed in a radial direction with respect to therotation axis S. The three rollers 57, 57, and 57 are disposed at equalintervals in a circumferential direction with respect to the rotationaxis S.

In addition, when the rotary disc 56 rotates around the rotation axis S,each of the rollers 57, 57, and 57 rotate around a roller rotation axisT. At this time, trajectories of each of the rollers 57, 57, and 57 areformed along the stirring flow path 55.

By rotation of the rotary disc 56 configured in this manner, compressionand relaxation of the stirring flow path 55 are repeated. As a result,the extraction sample having a particle interval adjusted due to thefirst extraction section 4A is in a random state again in the stirringflow path 55 as in the case of the whole sample.

Then, the stirred extraction sample flows through the discharge flowpath 53 and is fed to the second extraction section 4C.

Note that the stirring unit 52 illustrated in FIG. 12 or the like adoptsthe configuration of a peristaltic dosing pump. However, theconfiguration of the stirring unit 52 is not particularly limited, and aknown configuration may be used as long as the particle interval in theextraction sample can be in a random state again.

As described above, in the liquid feeding section 4B, the stirring unit52 adopts the configuration of a so-called peristaltic dosing pump, andcompresses and relaxes the stirring flow path 55. For this reason, apulsating flow is generated in the stirring flow path 55. Therefore, theparticle extraction microchip according to the present technology isconfigured such that the pair of dampers 54 absorbs the pulsating flowgenerated in the stirring flow path 55.

(3) Second Extraction Section

The extraction sample stirred by the stirring unit 52 flows through thedischarge flow path 53 and is fed to the second extraction section 4C.

This second extraction section 4C includes a sample inlet 61 forintroducing the extraction sample that has flowed through the dischargeflow path 53. This sample inlet 61 is connected to an extraction sampleflow path 62 through which the extraction sample flows. In addition, thesecond extraction section 4C includes a sheath liquid inlet 63 forintroducing a sheath liquid. This sheath liquid inlet 63 branches intotwo sheath liquid flow paths 64 and 64, and the sheath liquid flowsthrough these sheath liquid flow paths 64 and 64. Furthermore, thesesheath liquid flow paths 64 and 64 join the sample flow path 62 to formone main flow path 65. In this main flow path 65, a laminar flow of anextraction sample fed through the sample flow path 62 joins sheathliquid laminar flows fed through the sheath liquid flow paths 64 and 64to form a sheath flow in which the laminar flow of the extraction sampleis sandwiched between the sheath liquid laminar flows.

Furthermore, in the main flow path 65, an irradiation unit 7B irradiatesan extraction sample flowing in the main flow path 65, particularly atarget particle with excitation light. Fluorescence and/or scatteredlight emitted from the extraction sample by this irradiation with lightis detected by a light detection unit 8B. An optical signal detected bythis light detection unit 8B is converted into an electric signal andoutput to a driving unit 9B. This driving unit 9B adjusts pressure in apressure chamber 67 connected to the main flow path 65 and exhibits afunction of sending only a target particle to the pressure chamber 67.

Furthermore, the main flow path 65 branches into three flow paths on adownstream side. Specifically, the main flow path 65 branches into anextraction flow path 66 and two discarding flow paths 68 and 68. Amongthese flow paths, the extraction flow path 66 is a flow path for takingin a target particle which has been determined to satisfy predeterminedoptical characteristics by the driving unit 9B. In addition, thepressure chamber 67 for taking in only a target particle is disposed ona downstream side of the extraction flow path 66.

This pressure chamber 67 is connected to a storage flow path 69, and atarget particles in the pressure chamber 67 flows through the storageflow path 69 and is fed to a storage unit (not illustrated) in which thetarget particle is stored.

Meanwhile, a non-target particle which has been determined not tosatisfy the predetermined optical characteristics by the driving unit 9Bis not taken in the extraction flow path 66, and flows through eitherone of the two discarding flow paths 68 and 68. Thereafter, thenon-target particle is discharged to the outside through a discardingport 70.

In the second extraction section 4C as described above, the sample inlet61 corresponds to the sample inlet 42 in the first extraction section4A, the extraction sample flow path 62 corresponds to the sample flowpath 42 in the first extraction section 4A, the sheath liquid inlet 63corresponds to the sheath liquid inlet 43 in the first extractionsection 4A, the sheath liquid flow path 64 corresponds to the sheathliquid flow path 44 in the first extraction section 4A, the main flowpath 65 corresponds to the main flow path 45 in the first extractionsection 4A, the extraction flow path 66 corresponds to the extractionflow path 46 in the first extraction section 4A, the pressure chamber 67corresponds to the pressure chamber 47 in the first extraction section4A, the discarding flow path 68 corresponds to the discarding flow path48 in the first extraction section 4A, and the discarding port 70corresponds to the discarding port 49 in the first extraction section4A. The configurations thereof in the second extraction section 4C arethe same as those in the first extraction section 4A. In addition, theirradiation unit 7B corresponds to the irradiation unit 7A in the firstextraction section 4A, the light detection unit 8B corresponds to thelight detection unit 8A in the first extraction section 4A, and thedriving unit 9B corresponds to the driving unit 9A in the firstextraction section 4A. The structures themselves thereof in the secondextraction section 4C are the same as those in the first extractionsection 4A.

However, in the second extraction section 4C, the irradiation unit 7B,the light detection unit 8B, the driving unit 9B, the extraction flowpath 66, and the pressure chamber 67 correspond to the second extractionunit of the present technology, and the same function as the secondextraction unit 12 of the particle extraction apparatus 1 illustrated inFIG. 1 is exhibited. That is, in the second extraction section 4C, onlya target particle is extracted from an extraction sample.

The microchip 4 configured as described above includes three substratelayers. The sample flow path 42, the sheath liquid flow 44, the mainflow path 45, the extraction flow path 46, the pressure chamber 47, thediscarding flow path 48, the sample flow path 62, the sheath liquid flow64, the main flow path 65, the extraction flow path 66, the pressurechamber 67, the extraction sample flow path 51, the stirring flow path55, and the discharge flow path 53 are formed by a substrate layer a₁ asa first layer and a substrate layer a₂ as a second layer (see FIG. 12).

Meanwhile, the sample inlet 41, the extraction sample flow path 51, thestorage flow path 68, and the discarding port 70 are formed by thesubstrate layer a₂ as the second layer and a substrate layer a₃ as athird layer.

This microchip 4 can be constituted by bonding substrate layers in whichthe main flow path 45 and the like are formed.

The main flow path 45 and the like can be formed in the substrate layersby injection molding of a thermoplastic resin using a die. As thethermoplastic resin, a plastic conventionally known as a material of amicrochip, such as polycarbonate, a polymethylmethacrylate resin (PMMA),cyclic polyolefin, polyethylene, polystyrene, polypropylene,polydimethylsiloxane (PDMS), or cycloolefin polymer, can be adopted.

As described above, in the microchip 4 according to the presenttechnology, the particle interval in the extraction sample is preferablyreturned to a random state by compressing and relaxing the stirring flowpath 55 with the stirring unit 52. Therefore, the substrate layer a₁with which each of the rollers 53 of the stirring unit 52 is in contactpreferably includes a relatively soft resin, and examples thereofinclude polydimethylsiloxane (PDMS).

Note that the layer structure of the substrate layer of the microchip 4is not limited to three layers.

The microchip 4 according to the present technology as described aboveincludes the first extraction section 4A and the second extractionsection 4C, includes a plurality of components for performingextraction, and therefore can extract a target particle at high speedwith high purity. In addition, the microchip 4 can perform an extractionoperation superimposed by the first extraction section 4A and the secondextraction section 4C, and is not configured so as to simply dispose aplurality of extraction mechanisms. Therefore, an increase in size ofthe microchip and an increase in cost can be avoided as much aspossible.

Furthermore, by setting the detection number λ of a whole sample perunit time in the first extraction section 4A such that the recoveryratio Y_(Cascode) is equal to or higher than the final desired recoveryratio Ys of a target particle, the microchip 4 according to the presenttechnology can extract the target particle with higher purity.

5. Particle Extraction Method According to First Embodiment

The present technology also provides a particle extraction method forextracting a target particle.

FIG. 14 is a flowchart of a particle extraction method according to afirst embodiment.

The method includes at least a first extraction step S2 and a secondextraction step S4, and may include a whole sample inflow step S1, astirring step S3, and a target particle storing step S5 as necessary.Each of the steps will be described below in accordance with the orderin which the steps are performed.

(1) Whole Sample Inflow Step

The particle extraction method according to the present technology mayinclude the whole sample inflow step S1 for allowing a whole samplecontaining a target particle to flow into the particle extractionapparatus 1 illustrated in FIG. 1, for example.

A method for allowing a whole sample to flow into the particleextraction apparatus 1 is not particularly limited. For example, amethod for compressing and relaxing a flow path through which the wholesample flows using the liquid feeding unit 16 and allowing the wholesample in the housing unit 14 to flow into the particle extractionapparatus 1 is considered.

(2) First Extraction Step

The whole sample that has flowed into the particle extraction apparatus1 is subjected to an extraction operation by, for example, the firstextraction unit 11 in the particle extraction apparatus 1 illustrated inFIG. 1.

In the first extraction step S2, as in the first extraction unit 11, anextraction sample containing a target particle is extracted withoutperforming abort processing.

Specifically, a sheath flow in which a laminar flow of the whole sampleis sandwiched between sheath liquid laminar flows is formed, andextraction is performed using a flow cytometry principle.

That is, as in the first extraction unit 11, a target particle in thesheath flow is irradiated with light to detect fluorescence and/orscattered light generated from the target particle, and only anextraction sample containing the target particle exhibitingpredetermined optical characteristics is separated.

In this first extraction step S2, as in the first extraction unit 11, adetection number λ of a whole sample per unit time is preferably setwithin a range satisfying the following Mathematical Formula 35.

$\begin{matrix}{Y_{Cascode} = {{R \cdot \frac{1 + {\lambda_{T}{T_{P}/2}}}{1 + {\lambda_{T}\left( {{T_{P}/2} + T_{D}} \right)}} \cdot R \cdot \frac{1 + {\lambda_{T\; 2}{T_{P}/2}}}{\begin{matrix}{1 + {\lambda_{T\; 2}\left( {{T_{P}/2} + T_{D}} \right)} +} \\{\left( {1 - e^{{- \lambda_{U\; 2}}T_{P}}} \right)/e^{{- \lambda_{U\; 2}}T_{P}}}\end{matrix}}} \geq Y_{S}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 35} \right\rbrack\end{matrix}$

Note that an extraction method in the first extraction step S1 is notparticularly limited, and a known method can be adopted as long as anextraction sample containing a target particle is extracted withoutperforming abort processing.

(3) Stirring Step

The particle extraction method according to the present technology mayinclude a stirring step S3 for stirring an extraction sample extractedin the first extraction step S2.

Specifically, in this stirring step S3, the molecular sample having aparticle interval adjusted in the first extraction step S2 is stirred,and the particle interval is in a random state again as in the case ofthe whole sample.

A stirring method in this stirring step S3 is not particularly limited,and examples thereof include a method for compressing and relaxing aflow path through which an extraction sample flows using a knownperistaltic dosing pump.

(4) Second Extraction Step

The particle extraction method according to the present technologyincludes the second extraction step S4 of extracting only a targetparticle from the extraction sample extracted in the first extractionstep S2.

In the second extraction step S4, as in the first extraction step S2,extraction is performed using a flow cytometry principle. That is, asheath flow in which a laminar flow of the extraction sample issandwiched between sheath liquid laminar flows is formed, a targetparticle in the sheath flow is irradiated with light to detectfluorescence and/or scattered light generated from the target particle,and only a target particle exhibiting predetermined opticalcharacteristics is separated.

In other words, in this second extraction step S4, similar extraction tothe second extraction unit 12 included in the particle extractionapparatus 1 illustrated in FIG. 1 is performed.

(5) Target Particle Storing Step

The particle extraction method according to the present technology mayinclude the target particle storing step S5 for storing a targetparticle as necessary.

In this target particle storing step S5, the target particle extractedin the second extraction step S4 is stored.

A method for storing a target particle is not particularly limited, anda known method can be adopted in consideration of a storage environmentsuitable for the target particle and the like. In a case where thetarget particle is a cell, for example, in the storing step S5,temperature adjustment suitable for storing the cell, culture, and thelike may be applied.

The particle extraction method according to the present technology iscompleted by completion of the target particle storing step S5.

The particle extraction method according to the present technologyincludes the first extraction step S1 and the second extraction step S2,includes a plurality of components for performing extraction, andtherefore can extract a target particle at high speed with high purity.

In addition, by setting the detection number λ of a whole sample perunit time in the first extraction step S1 such that the recovery ratioY_(Cascode) is equal to or higher than the final desired recovery ratioYs of a target particle, the particle extraction method according to thepresent technology can extract the target particle with higher purity.

6. Particle Extraction Method According to Second Embodiment

A second embodiment of the particle extraction method according to thepresent technology will be described with reference to FIG. 15.

In the particle extraction technology of the present disclosure, in acase where a ratio of a target particle in a whole sample is lower thana predetermined threshold value, the first extraction step S1 and thesecond extraction step S4 are preferably performed in a cascade manner(hereinafter referred to as “cascade method”). Meanwhile, in a casewhere the ratio of a target particle in a whole sample is higher thanthe predetermined threshold value, the first extraction step S1 and thesecond extraction step S4 are suitably performed in parallel forperforming extraction at high speed (hereinafter referred to as“parallel method”).

Therefore, the present technology also provides a particle extractionmethod capable of switching between the cascade method and the parallelmethod depending on a ratio of a target particle in a whole sample.

The method relates to a particle extraction method using the particleextraction apparatus 3 illustrated in FIG. 8.

Note that FIG. 15 is a flowchart illustrating an extraction switchingstep in the particle extraction method according to the secondembodiment.

In this particle extraction method, first, the first extraction unit 11and the second extraction unit 12 are set in a state of beingsubordinately connected (cascade method setting step S101).

Then, it is determined whether or not a user recognizes a ratio of atarget particle in a whole sample (S102). If the user does not recognizethe ratio (NO in S102), the process proceeds to a target particle ratiomeasuring step S103.

In this measuring step S103, the whole sample is allowed to flow intothe first extraction unit 11, and a ratio of a target particle ismeasured using the detection system 110 and the processing system 130 inthe first extraction unit 11. Note that a method for measuring a targetparticles is not particularly limited, and a known method can be used.

Then, when the ratio of a target sample in a whole sample is recognized(YES in S102), it is determined whether or not the ratio of the targetparticle is lower than a predetermined threshold value (S104).

Here, as described above, in the cascade method, the detection number λof a whole sample per unit time in the first extraction unit 11 ispreferably set within a range satisfying the following MathematicalFormula 36.

$\begin{matrix}{Y_{Cascode} = {{R \cdot \frac{1 + {\lambda_{T}{T_{P}/2}}}{1 + {\lambda_{T}\left( {{T_{P}/2} + T_{D}} \right)}} \cdot R \cdot \frac{1 + {\lambda_{T\; 2}{T_{P}/2}}}{\begin{matrix}{1 + {\lambda_{T\; 2}\left( {{T_{P}/2} + T_{D}} \right)} +} \\{\left( {1 - e^{{- \lambda_{U\; 2}}T_{P}}} \right)/e^{{- \lambda_{U\; 2}}T_{P}}}\end{matrix}}} \geq Y_{S}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 36} \right\rbrack\end{matrix}$

Meanwhile, in a case of the parallel method, the detection number λ of awhole sample per unit time in each of the extraction units 11 and 12 ispreferably set such that the recovery ratio Y_(Parallel) by theextraction units 11 and 12 is equal to or higher than the final desiredrecovery ratio Ys of a target particle as expressed by the followingMathematical Formula 37.

$\begin{matrix}{Y_{Parallel} = {{R \cdot \frac{M + {\lambda_{T}{T_{P}/2}}}{\begin{matrix}{M + {\lambda_{T}\left( {{T_{P}/2} + T_{D}} \right)} +} \\{M \cdot {\left( {1 - e^{{- \lambda_{U}}{T_{P}/M}}} \right)/e^{{- \lambda_{U}}{T_{P}/M}}}}\end{matrix}}} \geq Y_{S}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 37} \right\rbrack\end{matrix}$

From the above, in a case where a maximum event rate satisfyingMathematical Formula 36 is represented by “λ_(Parallel_max)” and amaximum event rate satisfying Mathematical Formula 35 is represented by“λ_(Cascode_max)”, the threshold value as a switching reference betweenthe cascade method and the parallel method is represented by a targetparticle ratio at which the recovery ratio Y_(Parallel) in the cascademethod and the recovery ratio Y_(Cascode) in the parallel method areequal to each other as expressed by the following Mathematical Formula38.

$\begin{matrix}{\lambda_{{Parallel}\;{\_\max}} = \lambda_{{Cascode}\;{\_\max}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 38} \right\rbrack\end{matrix}$

Then, in the determination step S104, if it is determined that the ratioof a target particles in a whole sample is lower than the thresholdvalue (NO in S104), the following Mathematical Formula 39 is satisfied,and therefore a change to the parallel method is performed (parallelmethod changing step S105).

Thereafter, extraction by the first extraction unit 11 and extraction bythe second extraction unit 12 are started (S106)

$\begin{matrix}{\lambda_{{Parallel}\;{\_\max}} \geq \lambda_{{Cascode}\;{\_\max}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 39} \right\rbrack\end{matrix}$

In such a case, the detection number λ of a whole sample per unit timein each of the extraction units 11 and 12 is preferably set such thatthe recovery ratio Y_(Parallel) by the extraction units 11 and 12 isequal to or higher than the final desired recovery ratio Ys of a targetparticle as expressed by the following Mathematical Formula 40.

$\begin{matrix}{Y_{Parallel} = {{R \cdot \frac{M + {\lambda_{T}{T_{P}/2}}}{\begin{matrix}{M + {\lambda_{T}\left( {{T_{P}/2} + T_{D}} \right)} +} \\{M \cdot {\left( {1 - e^{{- \lambda_{U}}{T_{P}/M}}} \right)/e^{{- \lambda_{U}}{T_{P}/M}}}}\end{matrix}}} \geq Y_{S}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 40} \right\rbrack\end{matrix}$

Meanwhile, if it is determined in the determination step S104 that theratio of a target particle in a whole sample is higher than thethreshold value (YES in S104), the following Mathematical Formula 41 issatisfied. Therefore, a switching operation is not performed, andextraction by the first extraction unit 11 and extraction by the secondextraction unit 12 are started by the cascade method (S106).

$\begin{matrix}{\lambda_{{Parallel}\;{\_\max}} < \lambda_{{Cascode}\;{\_\max}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 41} \right\rbrack\end{matrix}$

In such a case, the detection number λ of a whole sample per unit timein the first extraction unit 11 is preferably set within a rangesatisfying the following Mathematical Formula 42.

$\begin{matrix}{Y_{Cascode} = {{R \cdot \frac{1 + {\lambda_{T}{T_{P}/2}}}{1 + {\lambda_{T}\left( {{T_{P}/2} + T_{D}} \right)}} \cdot R \cdot \frac{1 + {\lambda_{T\; 2}{T_{P}/2}}}{\begin{matrix}{1 + {\lambda_{T\; 2}\left( {{T_{P}/2} + T_{D}} \right)} +} \\{\left( {1 - e^{{- \lambda_{U\; 2}}T_{P}}} \right)/e^{{- \lambda_{U\; 2}}T_{P}}}\end{matrix}}} \geq Y_{S}}} & \left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 42} \right\rbrack\end{matrix}$

The particle extraction method according to the second embodiment asdescribed above can switch between the parallel method and the cascademethod, and therefore can extract a target particle with high purity athigh speed depending on a ratio of the target particle in a wholesample.

Furthermore, in a case where the cascade method is selected, theparticle extraction method according to the second embodiment canextract a target particle at high speed with high purity. In addition,by setting the detection number λ of a whole sample per unit time in thefirst extraction unit 11 such that the recovery ratio Y_(Cascode) isequal to or higher than the final desired recovery ratio Ys of a targetparticle, the particle extraction method according to the secondembodiment can extract the target particle with higher purity.

Meanwhile, even in a case where the parallel method is selected, theparticle extraction method according to the second embodiment canextract a target particle at high speed with high purity. In addition, aplurality of extraction mechanisms is not simply disposed. Therefore, anincrease in size of the particle extraction apparatus and an increase incost can be avoided as much as possible.

Incidentally, in the particle extraction method according to the presenttechnology illustrated in FIG. 15, a ratio of a target particle in awhole sample is measured in the measuring step S103. However, byallowing a small amount of sample to flow in the detection system 110 inadvance, the ratio of a target particle in a whole sample may bemeasured. The measuring step S103 does not have to be included.

Note that the particle extraction apparatus according to the presenttechnology can have the following configurations.

(1)

A particle extraction apparatus including:

a first extraction unit for extracting, from a whole sample containing atarget particle, an extraction sample containing the target particlewithout performing abort processing; and

a second extraction unit for subjecting the extraction sample extractedby the first extraction unit to abort processing and extracting only thetarget particle.

(2)

The particle extraction apparatus according to (1), in which the firstextraction unit and the second extraction unit are formed as separatemembers, and after extraction by the first extraction unit, extractionby the second extraction unit is performed.

(3)

The particle extraction apparatus according to (1), in which the firstextraction unit and the second extraction unit are formed as the samemember, and after extraction by the first extraction unit, extraction bythe second extraction unit is performed.

(4)

The particle extraction apparatus according to (2) or (3), furtherincluding a stirring unit for returning a particle interval in anextraction sample extracted by the first extraction unit to a randomstate.

(5)

The particle extraction apparatus according to any one of (1) to (4),further including:

a measurement unit for measuring the content of a target particle withrespect to the whole sample; and

an extraction switching unit for switching an extraction operation bythe first extraction unit and an extraction operation by the secondextraction unit to a parallel operation on the basis of a measurementresult by the measurement unit.

In addition, the particle extraction method according to the presenttechnology can have the following configurations.

(6)

A particle extraction method including:

a first extraction step of extracting, from a whole sample containing atarget particle, an extraction sample containing the target particlewithout performing abort processing; and

a second extraction step of subjecting the extraction sample extractedby the first extraction unit to abort processing and extracting only thetarget particle.

(7)

The particle extraction apparatus according to (6), further including astirring step of returning a particle interval in the extraction sampleto a random state after the first extraction step is performed.

(8)

The particle extraction apparatus according to (6) or (7) furtherincluding an extraction switching step of performing the firstextraction step and the second extraction step in parallel on the basisof a ratio of a target particle with respect to the whole sample.

Examples

Hereinafter, the present technology will be described in more detail onthe basis of Examples. Note that Examples described below exemplifyrepresentative examples of the present technology, and the scope of thepresent technology is not narrowly interpreted by Examples.

As an Example, the inventors of the present application performedperformance comparison between a particle extraction apparatus forperforming extraction by a cascade method and a particle extractionapparatus for performing extraction by a parallel method.

Specifically, several parameters (parameters 1 to 4) were set on thebasis of the above derived mathematical formulas, and performancecomparison was performed. An effect of the particle extraction methodaccording to the present disclosure was indicated quantitatively.Results of the performance comparison based on the parameters areillustrated in FIGS. 16 to 19. Here, in each of the drawings, thehorizontal axis indicates an event rate, and the vertical axis indicatesa yield. Furthermore, in each of the drawings, the one-dot chain lineindicates a result of the parallel method, and the two-dot chain lineindicates a result of the cascade method.

FIG. 16 is a drawing substitution graph illustrating a result ofperformance comparison between the cascade method and the parallelmethod based on parameter 1. As parameter 1, setting was performed suchthat R=1.0, r=0.03, T_(p)=50 μs, and TD=75 μs.

As understood from FIG. 16, in the case of parameter 1, it was confirmedthat the cascade method could realize a higher yield than the parallelmethod all the time within a range of event rate=0 to 100 keps.

That is, for example, in a case where yield specification was 80%, itwas confirmed that operation was possible at about 35 keps in thecascade method.

FIG. 17 is a drawing substitution graph illustrating a result ofperformance comparison between the cascade method and the parallelmethod based on parameter 2. As parameter 1, setting was performed suchthat R=0.9, r=0.03, T_(p)=50 ρs, and TD=75 ρs.

As understood from FIG. 17, in the case of parameter 2, it was confirmedthat the parallel method could realize a higher yield within a range ofevent rate=0 to 5 keps and that the cascade method could realize ahigher yield within a range of event rate=5 k to 100 keps.

That is, for example, in a case where yield specification was 80%, itwas confirmed that extraction by the parallel method was advantageousand that operation was possible at about 4 keps.

Meanwhile, in a case where yield specification was 60% as a slightly lowvalue, it was confirmed that operation was possible at about 48 keps inextraction by the cascade method.

FIG. 18 is a drawing substitution graph illustrating a result ofperformance comparison between the cascade method and the parallelmethod based on parameter 3. As parameter 3, setting was performed suchthat R=1.0, r=0.10, Tp=50 μs, and TD=75 μs.

As understood from FIG. 18, in the case of parameter 3, it was confirmedthat the cascade method could realize a higher yield than the parallelmethod all the time within a range of event rate=0 to 100 keps.

That is, for example, in a case where yield specification was 80%, itwas confirmed that operation was possible at about 14 keps in thecascade method.

FIG. 19 is a drawing substitution graph illustrating a result ofperformance comparison between the cascade method and the parallelmethod based on parameter 4. As parameter 4, setting was performed suchthat R=0.9, r=0.10, T_(p)=50 μs, and TD=75 μs.

As understood from FIG. 19, in the case of parameter 4, it was confirmedthat the parallel method could realize a higher yield within a range ofevent rate=0 to 10 keps and that the cascade method could realize ahigher yield within a range of event rate=10 k to 100 keps.

That is, for example, in a case where yield specification was 80%, itwas confirmed that extraction by the parallel method was advantageousand that operation was possible at about 5 keps.

Meanwhile, in a case where yield specification was 60% as a slightly lowvalue, it was confirmed that operation was possible at about 20 keps inextraction by the cascade method.

REFERENCE SIGNS LIST

-   1, 2, 3 Particle extraction apparatus-   11 First extraction unit-   12 Second extraction unit

The invention claimed is:
 1. A particle extraction apparatus comprising:a first extraction unit configured to extract, from a whole samplecontaining a target particle, an extraction sample containing the targetparticle without performing abort processing; a second extraction unitconfigured to subject the extraction sample to abort processing andextracting only the target particle; and a stirring unit disposedbetween the first extraction unit and the second extraction unit,wherein the stirring unit comprises a pump configured to return aparticle interval in the extraction sample to a random state prior tobeing provided as input to the second extraction unit via a flow pathbetween the first extraction unit and the second extraction unit,wherein the first extraction unit and the second extraction unit are nota same extraction unit.
 2. The particle extraction apparatus accordingto claim 1, further comprising: a measurement unit configured to measurea ratio of a target particle with respect to the whole sample; and anextraction switching unit configured to switch an extraction operationby the first extraction unit and an extraction operation by the secondextraction unit to a parallel operation on the basis of a measurementresult by the measurement unit.
 3. The particle extraction apparatusaccording to claim 1, further comprising a tubular member coupledbetween the first extraction unit and the second extraction unit,wherein the flow path is through the tubular member.
 4. The particleextraction apparatus according to claim 3, wherein the pump isconfigured to compress and relax the tubular member to return theparticle interval in the extraction sample to a random state.
 5. Theparticle extraction apparatus according to claim 1, further comprisingat least one damper disposed between the first extraction unit and thesecond extraction unit along the flow path.
 6. The particle extractionapparatus according to claim 5, wherein the at least one dampercomprises: a first damper disposed between the first extraction unit andthe stirring unit; and a second damper disposed between the stirringunit and the second extraction unit.
 7. A particle extraction methodcomprising: extracting, from a whole sample containing a targetparticle, an extraction sample containing the target particle withoutperforming abort processing; changing a particle interval in theextraction sample, wherein changing the particle interval in theextraction sample comprises returning a particle interval in theextraction sample to a random state; and subjecting the extractionsample having the changed particle interval to abort processing andextracting only the target particle.
 8. The particle extraction methodaccording to claim 7, further comprising performing the first extractionstep and the second extraction step in parallel on the basis of a ratioof a target particle with respect to the whole sample.
 9. A particleextraction microchip comprising: a first extraction unit configured toextract, from a whole sample containing a target particle, an extractionsample containing the target particle without performing abortprocessing; a second extraction unit for subjecting the extractionsample to abort processing and extracting only the target particle; anda stirring unit disposed between the first extraction unit and thesecond extraction unit, wherein the stirring unit comprises a pumpconfigured to return a particle interval in the extraction sample to arandom state prior to being provided as input to the second extractionunit via a flow path between the first extraction unit and the secondextraction unit, wherein the first extraction unit and the secondextraction unit are not a same extraction unit.
 10. The particleextraction microchip according to claim 9, further comprising a tubularmember coupled between the first extraction unit and the secondextraction unit, wherein the flow path is through the tubular member.11. The particle extraction microchip according to claim 10, wherein thepump is configured to compress and relax the tubular member to returnthe particle interval in the extraction sample to a random state. 12.The particle extraction microchip according to claim 9, furthercomprising at least one damper disposed between the first extractionunit and the second extraction unit along the flow path.
 13. Theparticle extraction microchip according to claim 12, wherein the atleast one damper comprises: a first damper disposed between the firstextraction unit and the stirring unit; and a second damper disposedbetween the stirring unit and the second extraction unit.